Battery pack

ABSTRACT

An object of the present invention is to secure a space in a battery case to house battery cells or minimum gaps to allow swelling of battery cells, so that the battery cells can be held in the battery case without play.  
     A battery pack  1  connects in series and house a plurality of square pole-like battery cells  3  in a battery case  3 , the plurality of battery cells each having a battery lid  32  positioned at the front side thereof, wherein a negative pole side tab  37  that is connected to a battery can bottom  35  of a battery cell and extends to the battery lid side, an intermediate connection tab  36  connecting a positive side pole of the battery cell to a battery can bottom of adjacent another battery cell and a positive pole side tab  34  connected to a positive pole terminal part of said another battery cell are provided, and a cell side insulating sheet  50  is provided between the respective negative pole side tab, intermediate connection tab and the sides of respective battery cans  31 , and a projecting tab for pressing side edge parts  3 E extending in the front and back direction of the respective battery cells, upper corner ribs  13 , small ribs  21  and lower corner ribs  22  (side edge pressing part) are respectively provided on the inner face of the upper side case and on the inner face of the lower side case.

TECHNICAL FIELD

[0001] The present invention relates to a battery pack housing aplurality of square pole-like battery cells in a battery case, andparticularly to maintaining the stable state of housing the batterycells in the battery case.

BACKGROUND ART

[0002] A battery pack is used with various kinds of electronicappliances as a battery that is capable of being charged, and suchbattery pack houses one or a plurality of battery cells in a batterycase.

[0003] There are some battery cells that are of a flat square pole inshape, and it is efficient in terms of space for these battery cells tobe housed in a square pole-like battery case that is one size largerthan the battery cell.

[0004] In addition, the battery pack is provided with a negative poleside tab creeping over the side of a battery can from the battery canbottom to the battery can lid side in order to provide a batteryterminal at one end of the battery pack or in a region in the directionof one end thereof.

[0005] Further, in the case where a plurality of battery cells areconnected in series, an intermediate connection tab is provided forconnecting the battery can bottom with a positive pole terminal part ofadjacent another battery cell, and the intermediate connection tab isprovided to creep over the side of the battery can as does theabove-mentioned negative pole side tab.

[0006] Meanwhile, when these negative pole side tab and intermediateconnection tab are disposed creeping over the side of the battery can,there is interposed an insulation sheet in-between.

[0007] In addition, there are provided some battery packs in which theabove-mentioned negative pole side tab and the intermediate connectiontab are respectively divided in two, and PTC (positive temperaturecoefficient) is interposed between these divided tab piece and tab pieceso as to break supply of electric power when the temperature of thebattery cell becomes high.

[0008] Further, with the square pole-like battery cell, the centralportion of a rectangle tends to bulge out at a time of the battery cellbeing charged.

[0009] Because of the above-mentioned fact, the battery case needs to beformed to be one or two size as large as the outer shape of the batterycell.

[0010] However, in the case where the battery case is formed larger thanthe battery cell, there occurs a problem in which the battery cellbecome wobbly in the inside thereof.

[0011] When the battery cell becomes wobbly in the battery case, theabove-mentioned negative pole side tab and the positive pole side tabthat are connected to the battery terminal repeat deformation that leadsto a trouble in which these tabs are damaged as the battery terminal isconventionally fixed to the battery case.

[0012] In addition, when the battery cell become wobbly, theabove-mentioned negative pole side tab and the intermediate connectiontab move and shift from the insulation sheet, resultantly leading to atrouble such as a short circuit of power.

DISCLOSURE OF THE INVENTION

[0013] An object of a battery pack of the present invention is to securea space in a battery case for housing battery cells as well as gaps toallow minimum swelling of a negative pole tab and an intermediateconnection tab so as to prevent the housed battery from becoming wobbly.

[0014] The battery pack of the present invention is a battery pack forhousing in a battery case a plurality of square pole-like battery cellsby connecting them in series; the battery case being comprised of anupper case and a lower case, respectively in box shape, in such afashion that they are combined with each other; the plurality of batterycells, each having a battery lid positioned on the front side, beinghoused side by side in the left and right direction in theabove-mentioned battery case, comprising a negative pole side tab thatis connected to the battery can bottom of a battery cell and extends tothe battery lid side, an intermediate connection tab that connects apositive pole terminal part of the negative pole cell with the batterycan bottom of adjacent another battery cell and a positive pole side tabconnected to a positive pole terminal part of said another battery cell,with the abovementioned negative pole side tab and intermediateconnection tab being disposed both creeping over the sides of therespective battery cells and being divided into two of a can bottom sidetab and a battery lid side tab, respectively. And PTC (positivetemperature coefficient) is interposed between these can bottom side taband battery lid side tab and a cell side insulating sheet is providedbetween the respective negative side tabs, intermediate connection tabsand the sides of the respective battery cans, with side edge pressingparts for pressing side edge portions extending in the front and backdirection of the respective battery cells being respectively provided onthe inner face of the upper case and on the inner face of the lower casewhen the upper case and lower case are combined with each other.

[0015] Therefore, according to a battery pack of the present invention,since side edge pressing parts for pressing side edge portions extendingin the front and left direction of battery cells are provided in abattery case, it is possible to hold the battery cells in the way thatthe battery cells do not become wobbly when they are housed in thebattery case, and at the same time, since a predetermined gaps areformed between the central portions of the battery cells housed in thebattery case and a separator so that when the central portions of theupper surface and under surface of the battery case bulge out due toswelling of the battery cells at a time of the battery pack beingcharged, the above-mentioned gaps can absorb the amount of bulging, itis possible to prevent the whole of the battery case from swelling anddeforming.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a perspective view of the whole of a battery pack,showing an embodiment applied to the battery pack with four batterycells;

[0017]FIG. 2 is a perspective view of a battery case being exploded upand down;

[0018]FIG. 3 is a perspective view seen from the backward direction of astate in which the battery case is removed;

[0019]FIG. 4 is a perspective view shown by exploding two upper andlower pairs of the four battery cells and a separator in the upper andlower direction;

[0020]FIG. 5 is a perspective view of the four battery cells and asubstrate exploded in the front and back direction;

[0021]FIG. 6 is a perspective view of exploded two left and rightbattery cells and respective tabs;

[0022]FIG. 7 is a bottom view of an upper side case;

[0023]FIG. 8 is a plan view of a lower side case;

[0024]FIG. 9 is a perspective view of the separator obliquely seen fromthe upper front direction;

[0025]FIG. 10 is a perspective view of the separator seen obliquely fromthe lower front direction;

[0026]FIG. 11 is a cross-sectional diagram along an XI-XI line of FIG.9;

[0027]FIG. 12 is a cross-sectional diagram along an XII-XII line of FIG.9;

[0028]FIG. 13 is a perspective diagram, after cutting off the batterypack at the approximately central portion thereof, showing respectiveportions by exploding them up and down;

[0029]FIG. 14 is a cross-sectional diagram along an XIV-XIV line of FIG.1, showing an expanded portion thereof;

[0030]FIG. 15 is a cross-sectional diagram along an XV-XV line of FIG.1, showing an expanded portion thereof;

[0031]FIG. 16 is an enlarged cross-sectional view of the battery pack;

[0032]FIG. 17 is an enlarged longitudinal view of the battery pack beingcut off at a position including a battery terminal in the longitudinaldirection, showing the battery cells and separator that are not cut off;

[0033]FIG. 18 is an enlarged longitudinal cross-section view of thebattery pack being cut off at a position including the battery pack inthe longitudinal direction;

[0034]FIG. 19 is a cross-sectional diagram by enlarging an openingperipheral edge of the upper side case;

[0035]FIG. 20 is a cross-sectional diagram by enlarging an openingperipheral edge of the lower side case;

[0036]FIG. 21 is a cross-sectional diagram showing an enlarged state ofthe opening peripheral edge of the upper side case and the openingperipheral edge of the lower side case being joined with each other;

[0037]FIG. 22 is a cross-sectional diagram showing a state in whichultrasonic welding is applied to the state of FIG. 1;

[0038]FIG. 23 is a plan view schematically showing a state of thebattery pack being placed on a receiving platform of an ultrasonicwelding device; and

[0039]FIG. 24 is a side view partially showing a cross-sectional stateof the battery pack being placed on the receiving platform of theultrasonic welding device.

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] Hereinafter, a battery pack 1 of the present invention will beexplained in detail according to embodiments shown in the followingdrawings.

[0041] The battery pack 1 comprises a square pole-like battery case 2,four battery cells 3, 3 . . . , a separator 4 to separate the batterycells 3, 3 that are disposed upward and downward out of the batterycells 3, 3 . . . , a substrate 6 on which an IC chip 5 is mounted tocompute and store the remaining amount of the battery pack 1 and abattery terminal 7 that is exposed from one end surface (front endsurface) in the longitudinal direction of the battery case 2 attachedonto the substrate 6 (refer to FIG. 2).

[0042] By the way, the U direction, the D direction, the L direction,the R direction, the F direction, the B direction that are indicated byarrow marks in respective drawings denote the upward direction, thedownward direction, the left direction, the right direction, the frontdirection and the back direction, respectively. In addition, theabove-mentioned directions indicated in this specification are forconvenience' sake and are subject to being changed depending on thecircumstances in which the battery pack 1 is used.

[0043] The four battery cells 3, 3 . . . are provided in a way that theyare superposed one on top of another in the up and down direction, andthe left and right direction, which will be described in detail lateron. Two of a battery cell 3 r ( ┌r┘ denotes the right side. Same asabove.) and a battery cell 31 ( ┌l┘ denotes the left side. Same asabove.) are combined with each other with a double-faced adhesive sheetmaterial 8 serving as an insulating member. These cells are connectedwith each other in series, which will be described later on, andfurther, two of upper side left and right battery cells 3 ur, 3 ul ( ┌u┘denotes the upper side. Same as above) and two of lower side left andright battery cells 3 dr, 3 dl ( ┌d┘ denotes the lower side. Same asabove) are connected in parallel by a circuit pattern (not shown) formedon the substrate 6.

[0044] The battery case 2 has an upper side case 10 and a lower sidecase 20, both of which are shaped like a box, and is constituted suchthat the upper side case 10 and the lower side case 20 are combined witheach other with respective openings thereof made to join with each other(refer to FIG. 2).

[0045] The inside dimensions in the left and right direction of theupper side case 10 and the lower side case 20 are approximatelyequivalent to or slightly greater than the left and right width of twoof the battery cells 3 ur, 3 ul that are disposed in the left and rightdirection, and the inside height of the upper side case 10 is formedgreater than the height dimension of one battery cell 3 with the insideheight of the lower side case 20 formed smaller than the heightdimension of one battery cell 3. When the upper side and lower sidecases are combined as the battery case 2, the height of the inside spaceis formed approximately equivalent to or slightly greater than theheight of two of the battery cells 3 u, 3 d that are superposed one ontop of another through the separator 4 (refer to FIG. 13).

[0046] In the central portion of the upper side case 10, there areformed a stepped difference part 11 slightly long in the front and backdirection with the front face side thereof being formed concave and theinner face side formed convex, and a projecting part 12 approximately onthe central portion of the inner face side of the stepped difference.The projecting part 12 is formed at positions corresponding to upperside adjacent side edge parts 3E, 3E of two of the battery cells 3 ur, 3ul that are provided upper side left and right, which will be describedlater on, so as to press these upper side edge parts 3E, 3E from theupper direction (refer to FIG. 13).

[0047] At upper corner portions on the left and right inner face sidesof the upper side case 10, there are formed small ribs (hereinafter, tobe referred to as ┌upper corner rib┘) 13, 13, . . . (refer to FIG. 7),and the upper corner ribs 13, 13, . . . press, from the upper direction,the upper side side edge parts 3E, 3E of the upper side battery cells 3ur, 3 ul housed in the battery case 2 (refer to FIG. 13).

[0048] In the central portions of the left and right portions of thelower inner face of the lower side case 20, there are provided smallribs 21, 21 . . . extending in the left and right direction and atappropriate intervals in the front and back direction (refer to FIG. 8), and the small ribs 21, 21 . . . are provided at positionscorresponding to lower side adjacent side edge parts 3E, 3E of two ofthe battery cells 3 dr, 3 dl disposed in the lower side left and rightdirection, which will be described later on, so as to press from thelower direction the lower side side edge parts 3E, 3E housed in thebattery case 2 (refer to FIG. 13).

[0049] At lower corner portions on the left and right inner face sidesof the lower side case 20, there are formed small ribs (hereinafter, tobe referred to as ┌lower corner rib┘) 22, 22, . . . (refer to FIG. 8),and the lower corner ribs ) 22, 22, . . . press from the lower directionthe lower side side edge parts 3E, 3E of the lower side battery cells 3dr, 3 dl when the battery cell 3 is housed in the battery case 2 (referto FIG. 13).

[0050] By the way, the projecting part 12 and the upper corner ribs 13of the upper side case 10 and the lower corner rib part 22 and the smallribs 21 of the lower side case 20 correspond to ┌side edge pressingpart┘ in claims.

[0051] A rectangular cutaway 23 is formed to open at a position that isthe front face and is biased to the right side from the central portionin the left and right direction of the front face and at the front endportion of the undersurface continuous from the biased portion, and theabove-mentioned battery terminal 7 is slid from the upper direction andattached to the rectangular cutaway 23, with the front face of thebattery terminal attached to the rectangular cutaway 23 being made to beapproximately flush with the lower side case 20 (refer to FIG. 17).

[0052] A stepped difference is formed at the peripheral edge of anopening of the lower face of the upper side case 10 to face in the innerand lower directions, and a peripheral wall (hereinafter, referred to as┌outer peripheral wall┘) 14 made thin of the upper side case is formedwith a taper part 14 a being formed at the inside edge of the lower endedge of the outer peripheral wall (refer to FIG. 19).

[0053] The upper surface of the stepped difference is formed into aninclined plane biased in the lower direction as the upper surface goesinside, and an inside portion having the inclined plane is formed into acircular projecting bar (hereinafter, referred to as ┌inside projectingbar┘)15, with the result that circular v groove 16 opening in the lowerdirection is formed between the inside projecting bar 15 and theabove-mentioned outer peripheral wall 14 (refer to FIG. 19).

[0054] In addition, the bottom (upper surface) 16 a of the v groove 16is formed into a horizontal plane that is narrow in width with a taperpart 15 a being formed at the inside edge of the above-mentioned insideprojecting bar 15 (refer to FIG. 19).

[0055] A stepped difference facing in the outer and upper directions isformed at the upper peripheral edge of an opening of the lower side case20, and a peripheral wall (hereinafter, referred to as ┌inner peripheralwall┘) 24 made thin of the inside of the lower side case 20 is formed,with the upper end of the inner peripheral wall 24 formed into a smallinclined plane (hereinafter, referred to as ┌outside inclined plane┘) 25on the outside thereof and a comparatively large inclined plane(hereinafter, referred to as ┌inside inclined plane┘) 26 on the insidethereof. The angle of the inside inclined plane relative to the verticaldirection is formed slightly smaller than that of the inclined plane ofthe inside projecting bar 15 that forms the v groove 16 of theabove-mentioned upper side case 10 (refer to FIG. 20). Meanwhile, theconcrete shapes of respective portions (numerical values) will bedescribed later on.

[0056] The battery cell 3 is shaped like a flat rectangular solid andcomprises a battery can 31 with one end thereof opening in thelongitudinal direction, a battery lid 32 to cover the opening of thebattery cell 31, a battery device and the like, not shown in thefigures, to be housed in the battery can 31, and a positive poleterminal parts 33 is provided in the battery lid 32 (refer to FIG. 6).

[0057] In addition, the positive pole terminals 33, 33 . . . provided inthe battery lids 32, 32, . . . of the respective battery cells 3, 3, . .. are provided at positions biased in one direction from the centralportion of the left and right direction, and two of the battery cells 3r, 3 l disposed left and right are combined with each other in a waythat the positive pole terminals 33 r, 33 l are oriented in a positionalrelationship to distance themselves from each other (refer to FIG. 6).

[0058] Further, since the two left and right battery cells 3 ur, 3 uland 3 dr, 3 dl connected in series of two up-and-down pairs of thebattery cells are such that the up and down battery cells areconstituted the same, an explanation will be given to one (up side) twoleft and right battery cells 3 ur, 3 ul, and a detailed explanation ofthe other (lower side) two left and right battery cells 3 dr, 3 dl willbe omitted.

[0059] In examining the two left and right battery cells 3 ur, 3 ul froman electrical view point, the right side battery cell 3 ur of thebattery cells arranged in series is connected to the positive pole side,and the left side battery cell 3 ul is connected to the negative poleside, respectively (refer to FIG. 6).

[0060] A positive pole side tab 34 with its tip extending rightward andbeing folded back forward is attached to a positive pole terminal part33 ur by spot welding (refer to FIGS. 4 and 6), with the tip portionthat was folded back forward serves as a lead part 34 a to be solderedto the above-mentioned substrate 6 (refer to FIG. 2).

[0061] An insulating sheet (cell side insulating sheet) 50 that isapproximately equivalent in size to the whole surface excluding left andright both side edges of the battery cells 3 ur, 3 ul is attached ontothe upper surface of the two battery cells 3 ur, 3 ul that are disposedleft and right, and a long aperture opening (hereinafter, referred to aslong-aperture opening) 51, from which a combined portion of the two leftand right battery cells is exposed is formed approximately in thecentral portion of the cell side insulating sheet 50. In addition, afolded part 52 folded downward for covering part of the battery lid 32is formed at the front edge of the insulating sheet 52 (refer to FIG.6). By the way, the portion between the left and right both side edgesof the cell side insulating sheet 50 and the left and right both sideedges of the battery cells 3 ur, 3 ul corresponds to ┌flank portion ofthe insulating sheet┘ in claim 3, and the above-mentioned long apertureopening 51 also corresponds to ┌flank portion of the insulating sheet┘in claim 3.

[0062] Then, in the right side battery cell 3 ur, there is provided anintermediate collection tab 36 that extends from a can bottom 35 ur ofthe battery cell 3 ur to the side of a battery lid 32 ur and creeps overthe upper side face of a battery can 31 ur through the above-mentionedcell side insulating sheet 50, the intermediate connection tab 36 beingdivided into two consisting of a can bottom side tab 36 a and a batterylid side tab 36 b in the front and back direction (refer to FIG. 6),with the end portion of the battery bottom side tab 36 a beingspot-welded to the can bottom 35 ur of the right side battery cell 3 ur(refer to FIG. 3). Further, the end portion of the battery lid side ofthe above-mentioned battery lid side tab 36 b, after extending in theleft direction, is folded downward to creep over a battery lid 32 ul,extending to a positive pole terminal part 33 ul of a left side batterycell 3 ul and is spot-welded to the positive pole terminal part 33 ul(refer to FIG. 4).

[0063] In addition, in the left side battery cell 3 ul, there isprovided a negative side tab 37 that extends from a can bottom 35 ul tothe side of a battery lid 32 ul and creeps over the upper side face of abattery can 31 ul through the above-mentioned insulating sheet 50, thenegative pole side tab 37, as is the above-mentioned intermediateconnection tab 36, being divided in two consisting of a can bottom sidetab 37 a and a can lid side tab 36 b in the front and back direction(refer to FIG. 6), with the end portion of the above-mentioned canbottom side 37 a spot-welded to the can bottom 35 ul of the left sidebattery cell 3 ul (refer to FIG. 3). Further, the end portion of thebattery lid side of the above-mentioned battery lid side tab 36 b hasthe front end thereof folded downward and then folded forward on thefront face side of the battery lid 32 of the left side battery cell 3ul, with the tip portion folded forward serving as a lead part 37 c bybeing soldered to the above-mentioned substrate 6 (refer to FIGS. 2 and4).

[0064] As a result, since the above-mentioned cell side insulating sheet50 is interposed between the intermediate connection tab 36, thenegative side tab 37 and the battery cans 31 ur, 31 ul, insulation isestablished between the battery cans 31 ur, 31 ul and the intermediateconnection tab 36, the negative pole side tab 37, particularly between abattery lid side tab 36 b and 37 b of the respective tabs 36 and 37(refer to FIG. 6).

[0065] PTC 38, 38 are interposed between the can bottom side tabs 36 a,37 a respectively divided into two in the front and back direction ofthe above-mentioned intermediate connection tab 36 and the negative poleside tab 37 and the battery lid side tab 36 b, 37 b, so that supply ofpower is shut off when the battery cells 3 ur, 3 ul become heated high(refer to FIG. 6).

[0066] Another insulating sheet (upper side insulating sheet) 53,approximately the same size of the above-mentioned cell side insulatingsheet 50, is further attached onto the upper surface of the two left andright battery cells 3 ur, 3 ul over which these intermediate connectiontab 36 and the negative side tab 37 creep (refer to FIG. 6).

[0067] Specifically, the upper side insulating sheet 53 has rectangularopenings (hereinafter, referred to as ┌rectangular opening┘) 54, 54formed at the positions corresponding to the region where the bottomside tabs 36 a, 37 a and the battery lid side tabs 36 b, 37 b, of theabove-mentioned intermediate tab 36 and the negative side tab 37 areconnected with each other through the PTC 38, 38. Further, at theposition corresponding to the long-aperture opening 51, there is formeda long-aperture opening 55 that is the same size of the long-apertureopening 51 (refer to FIG. 6). By the way, the portions between the leftand right both side edges of the upper side insulating sheet 53 and theleft and right both side edges of the battery cells 3 ur, 3 ulcorrespond to ┌flank portion of the insulating sheet┘ in claims, and theabove-mentioned long-aperture opening 55 corresponds to ┌flank portionof the insulating sheet┘ in the scope of claims, and further, theabove-mentioned rectangular openings 54, 54 corresponds to ┌flankaperture in the insulating sheet┘ in claim 5.

[0068] Then, adhesive material is applied onto the surface of such upperside insulating sheet 53, which is attached onto the cell sideinsulating sheet 50 on the above-mentioned battery cells 3 ur, 3 ul soas to sandwich the above-mentioned intermediate connection tab 36 andthe negative side tab 37.

[0069] As a result, the intermediate connection tab 36 and the negativepole side tab 37 are almost fixed on the side of the upper surface ofthe two battery cells 3 ur, 3 ul by being disposed in a way that they donot move easily, and the portions at which the can bottom side tabs 36a, 37 a and the battery lid side tabs 36 b, 37 b and the PTC 38, 38 areconnected, that is, the portions where thickness in the up and downdirection becomes thicker are exposed in the upper direction from therectangular openings 54, 54 of the upper side insulating sheet 53 (referto FIG. 4).

[0070] In the separator 4, a flat plate part 40 whose plane face isalmost the same as that of the two battery cells 3 r, 3 l disposed leftand right, two substrate regulating pieces 41, 41 provided to project atthe left and right corner portions of the front end edge of the flatplate part 40 to extend in the up and down direction thereof and batterycells regulating pieces 42, 42 projected in the up and down direction atthe back end edge of the above-mentioned flat plate part 40 so as tocorrespond to the can bottoms 35, 35, . . . of the respective batterycells 3, 3, . . . are integrally formed (refer to FIG. 9).

[0071] The substrate regulating pieces 41, 41 are ones for securing aspace in the front side within the battery case 2 so as to house theabove-mentioned substrate 6 when the separator 4 is housed in thebattery case (refer to FIGS. 17 and 18).

[0072] The two battery regulating pieces 42, 42 formed at the back endedge of the flat plate part 40 are ones for determining the positions inthe front and back direction of the two left and right battery cells 3ur (dr) , 3 ul (dl)(of upper side and lower side) with the can bottoms35, 35 . . . of the two battery cells coming in contact therewith (referto FIGS. 17 and 18). Further, the portions projecting downward of thebattery cell regulating pieces 42, 42 have rectangular cutaways formedin the central portions thereof, with the result that the can bottomside tabs 36 a, 37 a of the lower side two battery cells 3 dr, 3 dl donot interfere with the battery cell regulating pieces 42, 42 (refer toFIG. 3).

[0073] On the upper surface of the flat plate part 40 of the separator4, there are an upper surface central flat projecting bar 43 in thecentral portion thereof, extending in the front and back direction,upper surface left and right flat projecting bars 44, 44 at the left andright both side edges of the projecting bar 43, extending in the frontand back direction, all of them being integrally formed with separator4, and flat projecting parts 43 a, 43 a, 44 a, 44 a, . . . furtherslightly projecting upward are formed at the front end and back endportions of the respective flat convex parts 43 a, 43 a, 44 a, 44 a(refer to FIG. 9).

[0074] Meanwhile, the positions where the respective flat convex parts43 a, 43 a, 44 a, 44 a, . . . are formed are made to correspond to thereference position in thickness dimension of the battery cell 3.

[0075] Namely, since the battery can 31 of the battery cell 3 is usuallyformed by draw processing, it is difficult to accurately process thethickness in the up and down direction of every position. Therefore, asfor the thickness (dimension in the up and down direction) of thebattery can 31, of the peripheral edge thereof seen flatways, it is acommon practice to choose several positions serving as referencedimensions and to mold the battery can 31 by increasing the accuracy ofdimensions at the reference positions.

[0076] As a result, these reference positions are accurately formedregions with respect to the thickness of the battery cell 3, andpressing the regions by the inner face of the battery case 2 does notinvite an emergence of dimensional errors of the both. Consequently, thebattery cell 3 can be pressed without play when it is housed in thebattery case 2.

[0077] On the under surface of the flat plate part 40 of the separator4, there are an under surface central flat projecting bar 45 in thecentral portion thereof, extending in the front and back direction, anunder surface left and right flat projecting bars 46, 46 at the left andright both side edges of the flat projecting bar 45, extending in thefront and back direction, all of them being integrally formed with theseparator 4, and further, flat convex parts 46 a, 46 a, . . . slightlyprojecting downward are formed at the front end and back end portions ofthe under surface left and right flat projecting bars 46, 46 (refer toFIG. 10). Meanwhile, such flat convex parts 46 a, 46 a, . . . are formedalso at the positions corresponding to the reference positions inthickness dimensions of the battery cell 3.

[0078] In addition, on the under surface of the flat plate part 40,there are formed flat concave parts (hereinafter, referred to as ┌undersurface flat concave parts┘) 47, 47 long in the front and back direction(refer to FIG. 10) between the above-mentioned under surface centralflat projecting bar 45 and each of the both left and right flatprojecting bars 46, 46, and the under surface flat concave parts 47, 47correspond to the portions where the can bottom side tabs 38, 38 and thebattery lid side tabs 36 a, 37 a and the PTC 38, 38 are connected witheach other, that is, the ones where thickness in the up and downdirection become thicker (refer to FIG. 13).

[0079] The two battery cells 3 r, 3 l disposed left and right asmentioned above are attached onto the upper surface side and the lowerface side of the separator 4 that is formed in this manner.

[0080] Specifically, a double-faced adhesive sheet 60 with tworectangular apertures 60 a, 60 a formed therein, that is one sizesmaller than the plane form of the battery cell 3, is attached onto theupper surface of the separator 4, and the two battery cells 3 ul, 3 urare placed thereon to eventually be attached onto the separator 4 (referto FIG. 4).

[0081] At this time the respective battery cells 3 ur, 3 ul are placedon the respective flat convex parts 43 a, 43 a, 44 a, 44 a, . . . at theboth sides in the front and back direction of the above-mentioned uppersurface central flat projecting bar 43 and the upper surface left andright flat projecting bars 44, 44, that is, the back end side edge parts3E, 3E and the front biased left and both side edge parts 3E, 3E come incontact with the separator 4 through the above-mentioned double-facedadhesive sheet 60. Therefore, the under surfaces of the battery cells 3ur, 3 ul are in the state of having gaps with the separator 4 (refer toFIGS. 14 and 15). By the way, the above-mentioned double-faced adhesivesheet 60 is graphically not shown in FIGS. 14 through 18.

[0082] A double-faced adhesive sheet 61 that is similar to thedouble-faced adhesive sheet 60 attached onto the above-mentioned uppersurface thereof is attached onto the under surface of the separator 4,and the two battery cells 3 dr, 3 dl are positioned thereunder toeventually be attached to the separator 4 (refer to FIG. 4).

[0083] At this time the respective flat convex parts 46 a, 46 a, . . .at both sides in the front and back direction of the above-mentionedunder surface central flat projecting bar 45 and the under surface leftand right flat projecting bars 46, 46 come in contact with the batterycells 3 dr, 3 dl, that is, the back end side edge parts 3E, 3E and thefront biased left and right both side end edge parts 3E, 3E come incontact with the separator 4. In addition, the portions where the canbottom side tabs 38 a, 37 a and the battery lid side tabs 36 b, 37 b andPTC 38, 38 are connected with each other, that is, the ones where thethickness in the up and down direction thereof becomes thicker arepositioned within the above-mentioned under surface flat concave parts47, 47 without coming in contact with the separator 4, and are in thestate of having predetermined gaps (refer to FIGS. 14 and 15). By theway, the above-mentioned double-faced adhesive sheet 61 is notgraphically shown in FIGS. 14 through 18.

[0084] An IC chip 5 is mounted on the left side of the substrate 6 thatis provided in front of the four battery cells 3, 3, . . . disposed inthe front and back, and the left and right, directions, and the batteryterminal 7 is mounted on the lower portion at the right side thereofwith an insulating sheet (hereinafter, referred to as ┌substrate sideinsulating sheet┘) 70 interposed between the substrate 6 and the fourbattery cells 3, 3, . . . (refer to FIG. 5).

[0085] In the substrate 6, land apertures 6 a, 6 a, . . . are formed atpositions corresponding to lead portions 34 a, 34 a, 37 c, 37 c of thepositive pole side tabs 34, 34 and the negative pole side tabs 37, 37 inthe above-mentioned respective battery cells 3, 3, . . . . Further, cutlines 71, 71, . . . are formed at positions corresponding to the landapertures 6 a, 6 a, . . . of the substrate 6 in the substrate sideinsulating sheet 70 (refer to FIG. 5).

[0086] Then the substrate 6 is assembled to the respective battery cellsin such a way that first of all, the lead parts 34 a, 34 a, 37 c, 37 cof the respective positive side tabs 34, 34 and the negative pole sidetabs 37, 37 are passed through the respective cut lines 71, 71 of thesubstrate side insulating sheet 70. And after being passed through therespective land apertures 6 a, 6 a, . . . of the substrate 6, therespective lead parts 34 a, 34 a, 37 c, 37 c projecting from the landapertures 6 a, 6 a, . . . of the substrate 6 are soldered onto thesubstrate 6 (refer to FIG. 2).

[0087] Consequently, the left and right two battery cells 3 r, 3 l ofthe four battery cells 3, 3, . . . are connected in series, and theupper side and lower side two pairs of the battery cells 3, 3, . . . areconnected in parallel (refer to FIG. 2).

[0088] By the way, a cutaway, not a cut line, is formed at a position inthe substrate side insulating sheet 70 as corresponds to the lead part37 c of the negative pole side tab 37 of the left upper side batterycell 3 ul (refer to FIG. 5). This is because the upper side edge portionof the substrate side insulating sheet 70 is positioned at the reverseside of the folded part 52 of the upper side insulating sheet 53 and thelead part 37 c of the negative pole side tab 37 of the left upper sidebattery cell 3 ul is positioned to creep over the front face of thefolded part 52.

[0089] Therefore, the four battery cells 3, 3, . . . to which thesubstrate 6 is attached in this manner are housed in the battery case 2,and the battery pack 1 is assembled in the following manner.

[0090] First the four battery cells 3, 3, . . . that are combined witheach other in the up and down, and left and right, directions are housedin the lower side battery case 20 from the upper direction.

[0091] At this time the battery terminal 7 is slide-inserted in therectangular cutaway 23 of the lower side case 20 from the upperdirection (refer to FIG. 2). As the result the battery terminal 7 ispositioned in the front and back, and the left and right, directionswith respect to the lower side case 20.

[0092] In addition, the lower side two battery cells 3 dr, 3 dl of thehoused four battery cells 3, 3, . . . are placed on the small ribs 21,21 and the lower corner ribs 22, 22, . . . of the lower side case 20,that is, only the left and right both side edge parts 3E, 3E of .thebattery cells 3 dr, 3 dl come in contact with the lower side case 20,leading to a state in which gaps emerge between the large portion of theunder surface of the battery cells 3 dr, 3 dl and the bottom of thelower case 20.

[0093] Next the upper side case 10 and the lower side case 20 are joinedwith each other so as to cover the battery cells 3, 3, . . . to combinethe both (refer to FIGS. 13 and 16).

[0094] First of all, the upper end edge of the inner peripheral edge 24formed at the opening edge of the lower side case 20 is engaged with theinside of the v groove 16 formed at the outer peripheral edge of theupper side case 10 (refer to FIG. 21).

[0095] At this time, since the taper part 14 a is formed inside theouter peripheral wall of the upper case 10, and the outside inclinedplane 25 is formed outside the inner peripheral wall 14 of the lowerside case 20, although the upper side case 10 and the lower side case 20are shifted in the front and back, and the left and right, directions intheir positional relationship, engagement of the v groove 16 with theupper end edge of the inner peripheral wall 24 can be performed withoutfail (refer to FIG. 21).

[0096] In this state the inner side face of the outer peripheral wall 14of the upper case 10 and the outside face of the inner peripheral wall24 come in contact with each other face to face in the way that the faceof the upper side case 10 and that of the lower side case 20 areapproximately flush with each other (refer to FIG. 21).

[0097] In addition, when the upper side case 10 is joined with the lowerside case 20, since the opening edge at the right front side of theupper side case 10 is pressed from the upper direction, positioning inthe up and down direction of the batter terminal 7 is performed in theway that the battery terminal 7 is held between the lower side case 20and the upper side case 10 to be fixed to the inside of the batter case2.

[0098] Next, ultrasonic welding is applied to the upper side case 10 andthe lower side case 20, and the both are combined with each other (referto FIGS. 23 and 24).

[0099] Specifically, the upper side case 10 and the lower side case 20in the state of being combined with each other are turned upside downand placed on a receiving platform 81 of an ultrasonic welding device 80(refer to FIGS. 23 and 24).

[0100] In addition, specific forms (numerical values) of respectiveportions of each of the opening peripheral edges of the upper side case10 and the lower side case 20 will be shown in FIGS. 19 and 20. Thesenumerical values are one example from first to last, and the presentinvention is not limited thereto.

[0101] The thickness of the upper side case is formed 1.0 mm, and thatof the outer peripheral wall 0.45 mm. The height from the v groovebottom 16 a of the outer peripheral wall 14 is formed 0.7 mm, and thewidth of the v groove bottom (horizontal plane) 16 a is formed 0.15 mm.The angle of the inclined plane forming the v groove 16 of the insideprojecting bar 15 is formed 42.0° relative to the vertical line, and theheight from the v groove bottom 16 a of the inside projecting bar 15 isformed 0.3 mm (refer to FIG. 19).

[0102] Further, the thickness of the lower side case 20 is formed 1.0mm, and that of the inner peripheral wall 24 of the lower side case 200.525 mm. The height of the inner peripheral wall is formed 1.2 mm, andthat of the region where the outside inclined plane 25 is formed is 0.3mm while that of the region where the inside inclined plane is formed is0.665 mm, and the angle of the inside inclined plane 26 relative to thevertical line 32.6° (refer to FIG. 20).

[0103] The above-mentioned receiving platform 81 has receiving jigs 82,82 to approximately surround the upper side case 10 from the front andback, and the left and right, four directions, with gaps of inasmuch as0.1 mm formed in-between (refer to FIGS. 23 and 24).

[0104] Next, a welding hone 83 of the ultrasonic welding device 80 ismade to come in contact with the upper surface of the lower side case 20that is turned upside down with appropriate contact pressure, andvibrations in predetermined frequencies are added thereto (refer to FIG.24).

[0105] As the result, the contact portions of the upper side case 10 andthe lower side case 20, that is, the bottom 16 a of the v groove 16 ofthe upper side case 10 and the tip portion of the inner peripheral wall24 of the lower side case 20 are welded (refer to FIG. 22).

[0106] In the case of the upper side case 10 and the lower side case 20in the above-mentioned dimensions, such welding is to be terminated whenthe amount of welding becomes 0.25 mm, that is, at the position in whichthe height in the welding direction is reduced by 0.25 mm (refer to FIG.22).

[0107] Since melted material, at the time of welding, of the upper sidecase 10 and the lower side case 20 flows into gaps between the bottom 16a of the v groove 16 of the upper side case 10 and the outside inclinedplane 25 of the inner peripheral wall 24 of the lower side case 20, aspace between the inclined plane of the v groove 16 and the insideinclined plane 26 of the inner peripheral wall 24, and to the taper part15 a of the inside projecting bar 15 of the upper case 10, superfluouswelding material scarcely protrudes to the inner face side of thebattery case 2 (refer to FIG. 22).

[0108] Such welding is performed to the position where the upper endedge of the inner peripheral wall 24 of the lower side case 20 is meltedby 0.25 mm in the height dimension, and since the inside face of theouter peripheral wall 14 of the upper side case 10 and the outside faceof the inner peripheral wall 24 are brought in slide-contact with eachother, the stepped difference part 11 is not generated between the faceof the upper side case 10 and that of the lower side case 20, whichmeans both the faces become approximately flush with each other, lendinga good appearance (refer to FIG. 22).

[0109] In addition, forming of a welding portion of 0.25 mm for thewidth of the upper side case 10 and the lower side case 20 is sufficientin terms of intensity, and in the case of welding of more than thatamount, melted material protrudes, lending a bad appearance.

[0110] Therefore, in the state of the four battery cells 3, 3, . . .being housed in the battery case 2, the left and right both side edgeparts 3E, 3E of the respective battery cells 3, 3, 3, . . . become thestate of being held between the battery case 2 and the separator 4, withgaps resultantly formed between the upper surface and the battery case2, and between the under surface of the respective battery cells 3, 3, .. . and the separator 4 (refer to FIGS. 14 and 15).

[0111] Specifically, since the under surface side left and right bothside edge parts 3E, 3E . . . of the upper side two battery cells 3 ur, 3ul come in contact with the flat convex parts 43 a, 43 a, 44 a, 44 arespectively formed in the front and back both end portions of the threeflat projecting bars (upper surface central flat projecting bar 43 andupper surface left and right flat projecting bars 44, 44) formed on theupper surface side of the separator 4 through the double-faced adhesivesheet 60, predetermined gaps are formed between the under surfaces ofthese upper side two battery cells 3 ur, 3 ul and the separator 4, andfurther, predetermined gaps are formed between the upper surface ofthese upper side two battery cells 3 ur, 3 ul and the above-mentionedinner side face of the upper side case 10 as the upper surface left andright both side edge parts 3E, 3E, . . . come in direct contact with theprojecting part 12 provided to project approximately in the centralportion of the inner side face of the upper side case 10 and the uppercorner ribs 13 (refer to FIGS. 14 and 15).

[0112] The upper surface side left and right both side edge parts 3E,3E, . . . of the lower side two battery cells 3 dr, 3 dl come in contactwith the flat convex parts 46 a, 46 a, . . . through the double-facedadhesive sheet 60, that are formed at the both front and back endportions respectively formed in the under surface side central flatprojecting bar 45 and the under surface side left and right flatprojecting bars 46, 46 on the under surface side of the separator 4,with predetermined gaps being resultantly formed between the uppersurface of these lower side two battery cells 3 dr, 3 dl and theseparator 4. Further, with both the under surface side left and rightside edges 3E, 3E thereof coming directly in contact with the small ribs21, 21 formed approximately in the central portion of the lower innerside face and the lower corner ribs 22, 22, predetermined gaps areformed between the under surface of the lower side two battery cells 3dr, 3 dl and the lower inner side face of the lower side case 20 (referto FIG. 14, FIG. 15).

[0113] Particularly, the gaps between the upper surfaces sides of therespective battery cells 3, 3, . . . and the battery case 2 or theseparator 4 are comparatively large, and in the gaps are positioned theabove-mentioned negative pole side tab 37 and the intermediateconnection tab 36. In spite of the negative pole side tab 37 and theintermediate connection tab 36 being positioned, further gaps can be hadtherebetween (refer to FIGS. 14 and 15).

[0114] Meanwhile, the contact between the respective side edge parts 3E,3E, . . . of the above-mentioned battery cells 3, 3, . . . and theseparator 4 is performed through the double-faced adhesive sheets 60, 61as mentioned above.

[0115] The distance between the tips of the upper corner ribs 13, 13, .. . and those of the lower corner ribs 22, 22, . . . opposed to eachother within the battery case 2 assembled as mentioned above and thedimensions in the height direction of the four battery cells 3, 3, . . .combined with each other through the separator 4 are formed to be thesame or in the way that the height of the battery cells 3, 3, . . . isslightly larger. Consequently, in the state of the battery cells 3, 3, .. . being housed in the battery case 2, the respective double-facedadhesive sheets 60, 61 are slightly crushed so that the battery cells 3,3, . . . do not become wobbly in the battery case 2.

[0116] Further, since the respective side edge parts 3E, 3E, . . . ofthe battery cells 3, 3, . . . are directly pressed by the projectingpart 12 of the upper side case 10, the upper corner ribs 13 (side edgepressing part), the lower corner ribs 22 (side edge pressing part) andthe small ribs 21 (side edge pressing part) of the lower side case 20,all provided in the inner side face of the battery case 2, the state ofthe battery cells 3, 3, . . . housed in the battery case 2 can be madefree from play, so that the battery cells 3, 3, . . . can be stably heldin the battery case 2.

[0117] Then, when the battery pack 1 is charged, since the battery can31 of each of the respective battery 3, 3, . . . is shaped like a flatsquare solid, the central portions of the upper surface and the undersurface thereof bulge out, but because of the above-mentioned gaps beingformed between the respective battery cells 3 and the upper side case10, the lower side case 20 or the separator 4, the amount of bulging ofthe battery cell 3 can be absorbed within the gaps, so that the whole ofthe battery case 2 never swells nor deforms (refer to FIGS. 16 and 18).In the meantime, the battery cells 3, 3, . . . shown in FIG. 16 and FIG.18 by a continuous line indicate bulging states of the battery cell 3,3, . . . and the battery cells 3, 3, . . . shown by a two-dot lineindicate the states before bulging thereof.

[0118] Further, in the embodiments mentioned above, explanations havebeen given of the case in which by joining the upper side battery case10 with the lower side battery case 20 in a way to cover the batterycells 3, 3, . . . , combination of them are performed by ultrasonicwelding with the opening peripheral edges of the both in the state ofbeing joined with other. However, the present invention is not limitedthereto as the two may be combined with each other by using adhesivematerial.

[0119] In addition to this, the specific forms and structures of therespective portions shown in the above-mentioned embodiments are onlyone example for implementing the present invention, and therefore, thetechnological scope of the present invention should not be limitedlyconstrued.

[0120] As is apparent from the descriptions made thus far, a batterypack of the present invention is a battery pack characterized byconnecting in series and housing a plurality of square pole-like batterycells in a battery case, the battery case comprising a respectivelybox-like upper side case and lower side case joined with each other, theplurality of the battery cells having battery lids respectivelypositioned on the front side thereof and lining up in the left and rightdirection to be housed in the above-mentioned battery case; whereinthere are provided a negative pole side tab extending to the battery lidside connected to the bottom of a battery can of a battery cell, anintermediate connection tab connecting a positive pole terminal part ofthe negative pole side battery cell to the bottom of a battery can ofadjacent another battery cell and a positive pole side tab connected toa positive pole side terminal part of said another battery cell, theabove-mentioned negative pole side tab and the intermediate connectiontab being provided to creep over the side of the battery can of each ofthe respective battery cells by being respectively divided into two canbottom side tab and battery lid side tab, with PTC (positive temperaturecoefficient) interposed between these can bottom side tab and batterylid side tab; and further, a cell side insulating sheet is providedbetween the respective negative pole side tab, the intermediateconnection tab and the side of each of the respective battery cans; andside edge pressing parts respectively are provided on the inner face ofthe upper side case and on the inner face of the lower side case topress the side edge portions extending in the front and back directionof the respective battery cells when the upper side case and the lowerside case are combined with each other.

[0121] Therefore, according to a battery pack of the present invention,since the battery pack has provided in a battery case side edge pressingparts to press the side edge portions extending in the front and backdirection of battery cells, the battery cells can be held without playwhen the battery cells are housed in the battery case, and predeterminedgaps are formed between the central portion of the battery cells housedin the battery case and a separator; and when the battery cells swell ata time of the battery pack being charged and the central portions of theupper surface and the under surface bulge out, since the above-mentionedgaps can absorb the amount of bulging, it is possible to prevent thewhole of the battery case from swelling and deforming.

[0122] According to the present invention, the above-mentioned negativepole side tab and intermediate connection tab are held between a cellside insulating sheet and another upper side insulating sheet attachedto the upper side thereof, the negative pole side tab and intermediateconnection tab are approximately fixed onto the upper surface side anddisposed in such a way that they do not move easily. Consequently, evenin the case where the battery case is accidentally dropped, there are nomovements of the negative pole side tab and intermediate connection tab,thereby preventing the trouble in which they come in contact with abattery can.

[0123] According to the present invention, since a flank portion isprovided in the above-mentioned cell side insulating sheet so that aside edge pressing part directly contacts with battery cells, it ispossible to stably hold the battery cells.

[0124] According to the present invention, flank apertures are providedin the regions of the above-mentioned upper side insulating sheet, thatcorrespond to the above-mentioned PTC, the amount of thickness of a canbottom side tab, PTC, a battery and lid side tab that are superposed upone on top another can be absorbed, if only a little, therebycontributing to thinning of the thickness of a battery pack.

1. A battery pack in which a plurality of square pole-like battery cellsare connected in series and housed in a battery case, characterized inthat: the battery case is comprised of a respective box-like upper sidecase and lower side case combined with each other, the plurality of thebattery cells each have a battery lid respectively positioned on thefront side thereof and are lined up in the left and right direction tobe housed in said battery case, a negative pole side tab extending tothe battery lid side connected to the battery can bottom of a batterycell, an intermediate connection tab connecting a positive pole terminalpart of the battery cell to the battery can bottom of adjacent anotherbattery cell, and a positive pole side tab connected to a positive poleside terminal part of said another battery cell are provided, saidnegative pole side tab and intermediate connection tab are provided tocreep over the sides of the battery cans of the respective batterycells, said negative pole side tab and intermediate connection tab arerespectively divided into two of a can bottom side tab and a battery lidside tab with PTC (positive temperature coefficient) interposed betweenthese can bottom side tab and battery lid side tab, an insulating sheet(hereinafter, referred to as ┌cell side insulating sheet┘)is providedbetween the respective negative pole side tab, intermediate connectiontab and the sides of the respective battery cans; and side edge pressingparts are respectively provided on the inner face of the upper side caseand on the inner face of the lower side case to press the side edgeportions extending in the front and back direction of the respectivebattery cells when the upper side case and the lower side case arecombined with each other.
 2. A battery pack according to claim 1,wherein said negative pole side tab and intermediate connection tab areheld between the cell side insulating sheet and another insulating sheet(hereinafter, referred to as ┌upper side insulating sheet┘) attachedonto the upper side thereof.
 3. A battery pack according to claim 1,wherein a flank portion is provided in said cell side insulating sheetfor the side edge pressing parts to directly come in contact with thebattery cells.
 4. A battery pack according to claim 2, wherein a flankportion is provided in said upper side insulating sheet for the sideedge pressing parts to directly come in contact with the battery cells.5. A battery pack according to claim 1, wherein flank apertures areprovided in regions corresponding to said PTC of said upper sideinsulating sheet.